摘要
为提高近场捕获的能力与灵活性,研究了一种利用镀膜光纤探针对纳米微粒进行近场捕获的方法。采用麦克斯韦应力张量和三维时域有限差分方法建立了近场中纳米微粒的作用力模型,通过光阱力与其他作用力的比较讨论了近场捕获的稳定性,并根据各轴向光阱力的分布情况分析了纳米微粒的捕获尺寸与捕获位置。结果表明,只有当微粒尺寸小于探针孔径时才存在捕获效果,探针尖端不同位置出现不同捕获过程,在光阱力的作用下微粒最终被捕获至孔径边缘并形成圆状分布。结合纳米定位与检测方法,设计了全光纤低损耗的光纤探针近场捕获系统,并对120nm的聚苯乙烯微粒进行了捕获实验。结果表明,采用极低的激光功率能把粒径为激光波长1/7的纳米微粒捕获至光纤探针尖端,并形成内径与探针孔径一致的圆环状分布。该计算与实验结果为近场纳米操作的实验研究打下了基础。
A near-field trapping method for nanoparticles by a metal-coated optical fiber probe is proposed to improve the nanomanipulation technology.By applying a Maxwell stress tensor and 3D Finite Difference Time Domain（FDTD） methods,the physical properties of trapping stability,particle sizes and trapping positions in the near-field trapping are revealed.The effect of trapping forces acted on a nanoparticle along three axis directions on the trapping positions is studied,and different trapping positions are generated in the aperture edge in polarization direction and the center surface of the probe tip.Numerical results indicate that the Near-field Scanning Optical Microscopy（NSOM） probe is able to trap nanoparticles in a circular shape with lower laser intensity（~1040 W/mm2） than that（~105 W/mm2） required by a conventional optical manipulator.A near-field optical trapping system using the tapered metal-coated fiber probe is designed.A NSOM probe,a polarized semiconductor laser and a laser scanning confocal microscope are applied to pushing the trapping resolution further down to 120 nm.In experiments,120-nm polystyrene particles are trapped in multi-circular shape with a minimum size of 400 nm at a resolution of λ/7（λ： laser wavelength） and d（d： tip diameter of NSOM probe）,respectively,which agrees well with the simulated result.The method proposed in the paper largely promotes the role of near-field optical manipulation.
出处
《光学精密工程》
EI
CAS
CSCD
北大核心
2011年第10期2355-2365,共11页
Optics and Precision Engineering
基金
国家自然科学基金重大研究计划重点项目(No.90923041)
机器人技术与系统国家重点实验室(哈尔滨工业大学)开放研究基金重点项目(No.SKLRS-2010-2D-10)
中央高校基本科研业务费专项资金资助项目(No.HIT.NSRIF.201171)
高等学校学科创新引智计划资助项目(No.B07018)
关键词
近场捕获
光阱力
三维时域有限差分法
麦克斯韦应力张量
光纤探针
near-field optical trapping
optical trapping force
three dimensional Finite Difference Time Domain（FDTD） method
Maxwell stress tensor
optical fiber probe
